Array of structures , unable to use

Question

I am trying to use array of structures to store the information of 5 books.I was reading a book that ia quite common in Indian sub-continent i.e. "Let us C" just to understand what is C so that i am uch prepare to study K&R.While i was trying to implement one of the example for array of structures, i make required changes in the example but still i am getting certain errors and i am unable to find the error.

#include<stdio.h>

//void inkfloat(); commented as i am not using any float variable
int main()
{
    int i;
    struct book
    { 
        char bookname[30];
        char authorname[30];
        int price;
        int book_id;
    };

    struct book b[5];

    for(i=0;i<=4;i++)
    {
        printf("Enter bookname,authorname, price and book_id for book");
        scanf("%s %s %d %d",&b[i].bookname,&b[i].authorname,&b[i].price,&b[i].book_id);
    }

    for(i=0;i<=4;i++)
    {
        printf(" %s  %s  %d  %d \n",b[i].bookname,b[i].authorname,b[i].price,b[i].book_id); 
    }

    return 0;
}

/*void inkfloat()
  {
  float a=0,*b;
  b=&a;
  a=*b;
  }*/

I am getting output as

Enter bookname,authorname, price and book_id for book shailendra
Enter bookname,authorname, price and book_id for book let us c
Enter bookname,authorname, price and book_id for bookEnter bookname,authorname, price and book_id for bookEnter bookname,authorname, price and book_id for bookyaswat kanetkar
 s, �, -1218811592, -1216872840 l, :, -1218241152, -1218240426 u, ~, -1216874216, 0 c, �, 134513259, 0 y, , -1218653802, -1217138700

Along with that i am unable to understand the use of inkfloat variable which according to the book is used when we are using float variable inside our code and if didn't use it when using float variable a error will come"Floating points format not linked"

i had seen An array of structures and other related questions on stackoverflow, but cant resolve what error i am having in my code.

reference on a char array ? Never seen it, I think people use char* instead since C considers arrays as pointer to their first element. Why do you add the "&" symbol ? According to scanf doc it's not required for char[]. cplusplus.com/reference/cstdio/scanf. — Ricola3D
– Ricola3D, Commented Jun 24, 2013 at 11:12
Some lecture about references and arrays here: stackoverflow.com/questions/1106957/pass-array-by-reference-in-c — Ricola3D
– Ricola3D, Commented Jun 24, 2013 at 11:13
@Ricola3D:As per suggestions i removed "&", but still getting the same error — shailendra
– shailendra, Commented Jun 24, 2013 at 12:15

Mihai Maruseac · Accepted Answer · 2013-06-24 11:11:11Z

3

The problem is that %s in scanf reads only until the first whitespace character. Thus, you cannot read let us C using this approach because it will stop after reading let.

Finally, the & character is used to get the address of a variable. When reading into vectors you don't need it before the name of the vector since it has already decayed into a pointer.

edited Jun 24, 2013 at 11:11

answered Jun 24, 2013 at 11:03

Mihai Maruseac

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Varvarigos Emmanouil · Accepted Answer · 2013-06-24 11:03:29Z

1

When you read strings in scanf you don't need to use "&" symbol.

answered Jun 24, 2013 at 11:03

Varvarigos Emmanouil

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suspectus · Accepted Answer · 2013-06-24 11:06:03Z

0

The array name is a pointer to the first element in the array. The address operator should not be applied to the character arrays in the scanf statement.

   scanf("%s %s %d %d", b[i].bookname, b[i].authorname, &b[i].price, &b[i].book_id);
                       ^^^            ^^^

answered Jun 24, 2013 at 11:06

suspectus

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Dayal rai · Accepted Answer · 2013-06-24 11:07:21Z

0

You are overlooking warning: format ‘%s’ expects type ‘char *’, but argument 2 has type ‘char (*)[30]’.Make parameter as char * in line calling scanf.

answered Jun 24, 2013 at 11:07

Dayal rai

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Shumail · Accepted Answer · 2013-06-24 11:21:13Z

0

You are not supposed to pass address of pointer in this case with scanf. Use scanf without &. Moreover, it's not good to use scanf for reading string since when a blank space character appears it stops reading. So when you input "Let us C", here there's blank space after Let so it doesn't work. A better option is to use gets that can be useful here. See reference documentation of gets for more details.

I hope this helps.

answered Jun 24, 2013 at 11:21

Shumail

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Avner Solomon · Accepted Answer · 2013-06-24 21:34:44Z

0

As said by the others you have 2 mistakes:

You use scanf which read until the first white space character instead of fscaf which read until the end of the line.
When passing CString or Arrays you don't need you use the '&' character since the literal of the variable b[i] in you case is already decayed to a pointer.

Your read code should be something like this:

for(i=0;i<5;i++)
{
    printf("Enter bookname,authorname, price and book_id for book");
    fgets(b[i].bookname,30,stdin);
    fgets(b[i].authorname,30,stdin);
    scanf("%d %d",&b[i].price,&b[i].book_id);
}

You can check the whole source on cfiddle: http://cfiddle.net/oZvbRm

answered Jun 24, 2013 at 21:34

Avner Solomon

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